An internal combustion engine includes an engine block that at least partially defines a plurality of cylinders. A piston is slidingly disposed within each of the cylinders and pivotally coupled to a crankshaft. As the crankshaft rotates, the pistons are caused to reciprocate within the cylinders between a top-dead-center (TDC) position and a bottom-dead-center (BDC) position. In a two-stroke engine, a complete engine cycle includes an intake/compression stroke (i.e., a stroke of the piston from BDC to TDC) and a power/exhaust/intake stroke (TDC to BDC) for every complete revolution of the crankshaft. In a four-stroke engine, a complete engine cycle includes an intake stroke (TDC to BDC), a compression stroke (BDC to TDC), a power stroke (TDC to BDC), and an exhaust stroke (TDC to BDC) for every two revolutions of the crankshaft.
In order to maintain proper spatial relationship between the pistons and the cylinders, the crankshaft of an engine should be constrained from axial movement relative to the engine block. In a conventional engine, the crankshaft is constrained from axial movement by way of one or more generally planar thrust bearings that are held within a channel of the engine block and engage opposing collars of the crankshaft. Although adequate for constraining movement of the crankshaft, lubrication of conventional thrust bearings can be difficult and unreliable. This difficulty increases as an axial load on the crankshaft increases, for example in applications that require the engine to be capable of tilting to steep angles and when a generator or other auxiliary device is connected to an end of the crankshaft. When lubrication of the thrust bearing breaks down, metal-to-metal contact can occur, which can result in damage and/or failure of the thrust bearing.
One attempt to improve lubrication of a thrust bearing is described in U.S. Pat. No. 6,276,834 (the '834 patent) issued to Byard on Aug. 21, 2001. In particular, the '834 patent discloses a thrust bearing having valleys on a side facing the sliding partner. The valleys form wedge-shaped volumes, with rounded peaks between adjacent valleys. The wedge-shaped volumes hold lubricating oil that is taken along in the rotational direction out of the valleys and toward the peaks, thereby increasing a lubricating effect and load-carrying capacity of the bearing.
Although the thrust bearing of the '834 patent may help to improve lubrication and load-carrying capacity, it may still be less than optimal. In particular, the valleys, being formed at the rotating interface, are deepest and provide the greatest lubrication under the lightest load. As the load increases, the peaks and valleys will flatten out, thereby reducing the lubricating effect under the heaviest loads. In addition, the thrust bearing of the '834 patent is described as being fabricated through a stamping process. Stamping processes are well known in the art as having large variability in feature size, making bearing-to-bearing performance also vary greatly.
The thrust bearing of the present disclosure addresses one or more of the problems set forth above.